Module builders have heretofore been provided, as for example shown in U.S. Pat. No. 3,961,572. With such a module builder it has been common practice to position the module builder at one end of the field and to have the cotton pickers picking cotton to travel to the module builder and dump the picked seed cotton into the module builder. The seed cotton is tramped in the module builder by the mechanical tramper and after the module has been formed, the module builder is raised up from the module and advanced off the module to a new location where the next module is to be formed. It has been found that the use of such a module builder in certain situations has a number of disadvantages. For example, in large fields where the capacity of the basket on the cotton picker is insufficient to permit the cotton picker to advance all the way through the field before refilling the basket, it has been necessary for a cotton picker to stop picking and to carry the cotton to the module builder and then to return to the same location to finish picking those rows of cotton. In addition, such an arrangement has made it necessary to form the modules in undesirable locations in order to make them more accessible to the cotton pickers. There is therefore need for a new and improved module builder which overcomes these disadvantages.